Previous investigations from this laboratory have demonstrated that human decidual tissue in vitro synthesizes and secretes prolactin which is indistinguishable from pituitary prolactin by chemical, immunologic, and receptor assay techniques. Since numerous clinical and experimental studies indicate that the prolactin in amniotic fluid is derived from an extra-pituitary source, these studies strongly suggest that decidua is the source of amniotic fluid prolactin. Using decidual organ and primary cell cultures as model systems, experiments are now proposed to investigate (1) the effects of extracellular ions and osmolality, progesterone, estrogen, prostaglandins, beta-endorphin, somatostatin and other factors on the synthesis and secretion of prolactin by normal pre-term and term decidua; (2) the physiologic roles of cyclic adenosine monophosphate and calcium as intracellular mediators in the regulation of the synthesis and secretion of decidual prolactin; and (3) the synthesis and secretion of prolactin by decidua to the stimulatory and inhibitory factors which affect prolactin production and release from normal term decidua. Decidua from patients with diabetes mellitus, pre-eclampsia, and intrauterine growth retardation will be studied since most patients with these conditions have abnormal amniotic fluid prolactin concentrations. Since decidua is the probable source of the prolactin in amniotic fluid, these studies should provide insight into the physiology and pathophysiology and amniotic fluid prolactin.